Iron-based alloy for making a golf club head

ABSTRACT

An iron-based alloy for making a golf club head includes: chromium in an amount ranging from 21.5 to 24.5 wt %; nickel in an amount ranging from 4.45 to 6.05 wt %; nitrogen in an amount ranging from 0.17 to 0.23 wt %; copper in an amount ranging from 1.5 to 3.5 wt %; carbon in an amount of greater than 0 wt % and not more than 0.06 wt %; and a balance of iron, based on a total weight of the iron-based alloy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an iron-based alloy, more particularly to an iron-based alloy for making a golf club head.

2. Description of the Related Art

Taiwanese Patent No I207743 discloses an iron-based alloy for making a golf club head which includes: chromium in an amount ranging from 21.8 to 24.8 wt %; nickel in an amount ranging from 7.8 to 8.8 wt %; nitrogen and carbon in an amount ranging from 0.03 to 0.12 wt %; and a balance of iron, based on a total weight of the iron-based alloy.

The ductility of the iron-based alloy can be increased by adding nickel so that the moldability of the golf club head can be improved. However, since the iron-based alloy disclosed in the prior art contains a relatively high amount of nickel, the overall mechanical strength of the iron-based alloy, especially the tensile strength, will be reduced. Therefore, the golf club head made therefrom is liable to be deformed.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide an iron-based alloy for making a golf club head which has improved tensile strength while still maintaining a satisfactory ductility.

Accordingly, in a first aspect of the present invention, an iron-based alloy for making a golf club head includes:

chromium in an amount ranging from 21.5 to 24.5 wt %;

nickel in an amount ranging from 4.45 to 6.05 wt %;

nitrogen in an amount ranging from 0.17 to 0.23 wt %;

copper in an amount ranging from 1.5 to 3.5 wt %;

carbon in an amount of greater than 0 wt % and not more than 0.06 wt %; and

a balance of iron, based on a total weight of the iron-based alloy.

In a second aspect of the present invention, a golf club head comprises an iron-based alloy including:

chromium in an amount ranging from 21.5 to 24.5 wt %;

nickel in an amount ranging from 4.45 to 6.05 wt %;

nitrogen in an amount ranging from 0.17 to 0.23 wt %;

copper in an amount ranging from 1.5 to 3.5 wt %;

carbon in an amount of greater than 0 wt % and not more than 0.06 wt %; and

a balance of iron, based on a total weight of the iron-based alloy.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:

FIG. 1 shows a metallograph of a cast product formed from a preferred embodiment of an iron-based alloy according to this invention in; and

FIG. 2 illustrates compositional distributions of various steel alloys and the iron-based alloy of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The iron-based alloy for making a golf club head according to this invention preferably includes: chromium in an amount ranging from 21.5 to 24.5 wt %; nickel in an amount ranging from 4.45 to 6.05 wt %; nitrogen in an amount ranging from 0.17 to 0.23 wt %; copper in an amount ranging from 1.5 to 3.5 wt %; carbon in an amount of greater than 0 wt % and not more than 0.06 wt %; silicon in an amount of greater than 0 wt % and not more than 1.0 wt %; manganese in an amount of greater than 0 wt % and not more than 1.0 wt %; and a balance of iron, based on a total weight of the iron-based alloy.

Addition of chromium into the iron-based alloy not only increases the corrosion resistance and the oxidation resistance of the iron-based alloy, but also enhances the hardenability and the high temperature strength of the iron-based alloy, and especially has a significant effect for abrasion resistance of high-carbon steel. Basically, chromium is for stabilizing the BCC ferritic phase. If the chromium amount in the iron-based alloy is lower than 21.5 wt %, the golf club head made of the iron-based alloy will have an insufficient ferritic phase, and thus will have unsatisfactory mechanical strength. If the chromium amount in the iron-based alloy is higher than 24.5 wt %, the golf club head made of the iron-based alloy will have an excess ferritic phase, and thus will have unsatisfactory ductility. During the production of the iron-based alloy, in order to easily control the microscopic structure of the iron-based alloy (austenitic matrix+6-17% ferritic particle distribution) for better performance of a golf club head, the chromium amount in the iron-based alloy should range from 21.5 wt % to 24.5 wt %. In a preferred embodiment, the chromium amount is 22.26 wt %.

Addition of nickel into the iron-based alloy not only increases the corrosion resistance and the oxidation resistance of the iron-based alloy, but also stabilizes the FCC austenitic phase. If the nickel amount in the iron-based alloy is lower than 4.45 wt %, the golf club head made of the iron-based alloy will have a relatively unstable austenitic phase and an excess ferritic phase, and thus has an unsatisfactory ductility. If the nickel amount in the iron-based alloy is higher than 6.05 wt %, although the austenitic phase can be stabilized, the ferritic phase will be insufficient. Therefore, the golf club head made of the iron-based alloy will have unsatisfactory mechanical strength. In order to easily control the microscopic structure of the iron-based alloy during the production of the iron-based alloy so as to make a golf club head having a superior performance, the nickel amount in the iron-based alloy should range from 4.45 wt % to 6.05 wt %. In a preferred embodiment, the nickel amount is 5.46 wt %.

Carbon and nitrogen are essential elements in a steel material, and are necessary to stabilize the austenitic phase. However, if the amount of carbon and nitrogen in the iron-based alloy is excessive, the corrosion resistance of the iron-based alloy will be unsatisfactory. Therefore, in order for the iron-based alloy to have a satisfactory corrosion resistance and a stable austenitic phase, the total amount of carbon and nitrogen in the iron-based alloy should range from 0.22 wt % to 0.28 wt %. The nitrogen amount in the iron-based alloy should range from 0.17 wt % to 0.23 wt %, and the carbon amount in the iron-based alloy should be greater than 0 wt % and not more than 0.06 wt %. In a preferred embodiment, the carbon amount is 0.04 wt % and the nitrogen amount is 0.19 wt %.

Addition of silicon into the iron-based alloy has advantages of preventing the formation of pores, enhancing the shrinkability, and increasing the fluidity of molten steel. However, if the silicon amount in the iron-based alloy is higher than 1.0 wt %, the golf club head made of the iron-based alloy will have unsatisfactory ductility. Therefore, the silicon amount in the iron-based alloy should be not more than 1.0 wt %. In a preferred embodiment, the silicon amount is 0.56 wt %.

Manganese usually co-exists with iron. Since manganese can be combined with sulfur easily, the thermal brittleness of the iron-based alloy due to the presence of sulfur can be eliminated. Furthermore, the oxide in the iron-based alloy can be removed by manganese. Additionally, the FCC austenitic phase can be stabilized by manganese. Therefore, addition of manganese into the iron-based alloy in an amount of greater than 0 wt % and not more than 1.0 wt % can eliminate the thermal brittleness of the iron-based alloy and improve the castability of the iron-based alloy. In a preferred embodiment, the manganese amount is 0.37 wt %.

As compared to the nickel amount in the iron-based alloy of the prior art, the nickel amount in the iron-based alloy of the present invention is relatively low so that the overall mechanical strength of the iron-based alloy, especially the tensile strength, can be improved while maintaining a reasonable ductility. An inclining angle of a striking face of the golf club head made of the iron-based alloy of the present invention can be adjusted in a range from −5 to +5′ without conducting any heat treatment. As a substitute for the reduced amount of nickel, copper is used in an amount ranging from 1.5 to 3.5 wt % to further enhance the overall mechanical strength of the iron-based alloy of the present invention. If the copper amount in the iron-based alloy is lower than 1.5 wt %, the overall mechanical strength for the golf club head will be insufficient. If the copper amount in the iron-based alloy is greater than 3.5 wt %, the corrosion resistance for the golf club head will be unsatisfactory. In a preferred embodiment, the copper amount is 2.38 wt %.

The iron-based alloy of the present invention can be used to manufacture a golf club head using, for example, a casting process well known in the art.

FIG. 1 shows a metallograph of a cast golf cub head formed from a preferred embodiment of an iron-based alloy according to this invention.

A comparison of examples of the iron-based alloy of the present invention with comparative examples of the prior art is shown in Table 1.

TABLE 1 Mechanical properties Composition Tensile Yield (wt %) strength Strength elongation No. Fe Cr Ni C N Si Mn Cu (Ksi) (Ksi) (%) Remark Ex. 1 Bal. 22.26 5.46 0.04 0.19 0.56 0.37 2.38 110 65 44 Casting Ex. 2 Bal. 23.38 4.72 0.05 0.23 0.60 0.51 2.92 115 72 42 Casting Ex. 3 Bal. 21.85 6.03 0.06 0.17 0.52 0.48 1.51 101 62 50 Casting Ex. 4 Bal. 24.16 4.48 0.03 0.23 0.63 0.52 3.02 116 71 40 Casting Comp. Bal. 23.30 8.54 0.05 0.06 0.51 — — 99.7 73.7 50.2 Casting + solid Ex. 1 Solution treatment, 4 hrs Comp. Bal. 24.45 8.89 0.04 0.04 — — — 97.1 72.3 50.4 Casting + Solid Ex. 2 Solution treatment, 4 hrs Comp. Bal. 20.45 8.14 0.06 0.04 — 0.78 — 78.2 55.2 43.3 Casting + Solid Ex. 3 Solution treatment, 4 hrs Comp. Bal. 26.15 9.89 0.05 0.03 0.23 0.43 — 118.1 77.2 43.1 Forging + Solid Ex. 4 Solution treatment, ½ hr

It is shown in Table 1 that, as compared to the prior art, without conducting any heat treatment, the present invention can provide a tensile strength and a yield strength substantially equal to or even higher than those of the prior art which must undergo solid solution treatment. Therefore, a golf club head having satisfactory mechanical properties can be made time-effectively through a simplified process using the iron-based alloy of the present invention.

FIG. 2 illustrates compositional distributions of various steel alloys and the present iron-based alloy.

In view of the aforesaid, a satisfactory combination of mechanical properties can be obtained by the iron-based alloy of the present invention in which the nickel amount is reduced as compared to the iron-based alloy of the prior art and copper is added as a substitute for the reduced amount of nickel.

While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

1. An iron-based alloy for making a golf club head, comprising: chromium in an amount ranging from 21.5 to 24.5 wt %; nickel in an amount ranging from 4.45 to 6.05 wt %; nitrogen in an amount ranging from 0.17 to 0.23 wt %; copper in an amount ranging from 1.5 to 3.5 wt %; carbon in an amount of greater than 0 wt % and not more than 0.06 wt %; and a balance of iron, based on a total weight of said iron-based alloy.
 2. The iron-based alloy as claimed in claim 1, further comprising silicon in an amount of greater than 0 wt % and not more than 1.0 wt % based on a total weight of said iron-based alloy.
 3. The iron-based alloy as claimed in claim 1, further comprising manganese in an amount of greater than 0 wt % and not more than 1.0 wt % based on a total weight of said iron-based alloy.
 4. The iron-based alloy as claimed in claim 1, further comprising silicon in an amount of greater than 0 wt % and not more than 1.0 wt %, and manganese in an amount of greater than 0 wt % and not more than 1.0 wt %, based on a total weight of said iron-based alloy.
 5. A golf club head, comprising an iron-based alloy including: chromium in an amount ranging from 21.5 to 24.5 wt %; nickel in an amount ranging from 4-45 to 6.05 wt %; nitrogen in an amount ranging from 0.17 to 0.23 wt %; copper in an amount ranging from 1.5 to 3.5 wt %; carbon in an amount of greater than 0 wt % and not more than 0.06 wt %; and a balance of iron, based on a total weight of said iron-based alloy. 